The proposed research will evaluate the immune response of a mosquito, Aedes trivittatus, against two different species of filarial worms, Brugia pahangi and Dirofilairia immitis. Basic experiments are designed to determine the characteristics of the immune response in terms of its rate, limitations, and effect on the developing filarial worm. Studies will elucidate the degree of specificity of the reaction, the relative importance of hemocytes and hemolymph in the response, and the importance of melanin production to the effectivness of the reaction. Experiments will attempt to determine if an induced immunity can occur in Ae. trivittatus, or if an active immune response will limit additional infections. Longevity experiments will test the possible effects the immune response may have in reducing or limiting parasite burdens, thereby increasing the mosquitoes chances for survival. Particular attention will be paid to the effect the immune response may have on the ability of the mosquito to function as a successful vector.